This invention relates generally to inflatable restraint systems and, more particularly, to the retention of an inflatable cushion, commonly referred to as an air bag, in such systems.
Safety restraint systems which self-actuate from an undeployed to a deployed state without the need for intervention by the operator, i.e., "passive restraint systems", and particularly those restraint systems incorporating inflatable bags or cushions, as well as the use of such systems in motor vehicles have been the subjects of much discussion as the desirability of the use of such passive restraint systems has gained general acceptance in the United States.
It is well known to protect a vehicle occupant using a cushion or bag that is inflated with gas, e.g., an "air bag", when the vehicle encounters sudden deceleration, such as in a collision. The term "air bag" is something of a misnomer, however, as during deployment the rapidly evolving gas with which the bag is filled is typically not air but rather an inert gas, e.g., nitrogen. In such systems, the cushion is normally housed in an uninflated and folded condition to minimize space requirements. In an emergency, gas is discharged from an inflator to rapidly inflate the bag. The cushion, upon inflation, serves to restrain the movement of the vehicle occupant as the collision proceeds. In general, such air bags are commonly designed to be inflated in no more than about 45-60 milliseconds.
Vehicular inflatable restraint systems generally include multiple crash sensors generally positioned about or mounted to the frame and/or body of the subject vehicle and serve to sense sudden decelerations by the vehicle. In turn, the sensor sends a signal to an inflatable air bag/cushion module or assembly strategically positioned within the riding compartment of the vehicle to actuate deployment of the cushion. In general, an inflatable cushion provided for the protection of a vehicle driver, i.e., a driver side air bag, is mounted in a storage compartment located in the steering column of the vehicle. Whereas, an inflatable cushion for the protection of a front seat passenger, i.e., a passenger side air bag, is typically mounted in the instrument panel/dash board of the vehicle.
Typical inflatable cushion restraint systems make use of an air bag module which generally includes an outer reaction housing or canister, commonly referred to as a "reaction can" or, more briefly, as a "can". The reaction canister generally serves to support or contain other components of the air bag module system, including what is referred to as a "air bag inflator" or, more briefly, as an "inflator" or, alternatively, as a "generator". The inflator, upon actuation, acts to provide the gas to inflate the air bag/cushion.
Inflators used in such systems are typically either of a pyrotechnic or hybrid type. Pyrotechnic inflators generally contain a gas generating material which, upon activation, generates gas used to inflate the air bag/cushion. In general, the inflation gas produced by a pyrotechnic inflator is emitted from openings or emission ports along the length of the inflator. In contrast, hybrid type inflators in addition to a body of ignitable pyrotechnic material generally contain as the primary inflation gas a stored, compressed gas which, upon proper actuation, is expelled from the inflator. As a consequence of the physics associated with the storage of compressed gases, the container used to store this compressed gas typically has a cylindrical shape. Furthermore, the discharge of gas from such a cylindrically shaped gas storage container typically occurs by way of openings or emission ports at only one end of the cylindrical container. To attain proper bag deployment, however, it is generally desired that the emission of gas into the air bag/cushion from such a storage container be done in a fairly uniform manner. With typical air bag/inflator assemblies, such uniform emission is generally attained by having a relatively even emission of gas into the deploying bag along the length of the gas inlet opening of the bag connected, directly or indirectly, to the inflator. In this way the bag is properly uniformly deployed and the risk of the bag deploying in a skewed manner due to the discharge of gas from only one end of the storage container is avoided.
The reaction housing typically is an open-mouthed container into which the air bag/cushion, in an uninflated and folded condition, is also placed. In practice and in prior art devices, the component parts of such inflatable restraining devices, particularly the inflatable air bag and the housing, are commonly joined and held together through the use of a multiple number of selected fasteners such as screws, rivets or bolts.
For example, a selected fastener is typically passed through fastener holes which have been preformed in the respective parts to be fastened together. Unfortunately, a problem frequently experienced in the assembly of these inflatable restraining units is difficulty in achieving and maintaining desired and proper fastener hole alignment of the respective parts to be fastened together. Also, in order to avoid undesired point loading of the stresses generated upon bag deployment, it is generally preferred to secure or fasten the bag into the assembly by means of fastening the bag between two load bearing materials (e.g., metals), such as between the reaction canister and metal retaining flanges or a metal ring placed about the gas inlet opening of the bag, for example. In this way, undesired loading of bag deployment stresses at or about the fastener holes in the bag fabric is reduced and preferably avoided.
In general, such fastening is done through the reaction canister itself, thereby simplifying the assembly process as the canister, bag and metal retaining flanges or metal ring are all simultaneously fastened together by means of such fastening. Unfortunately, it is difficult to simultaneously maintain proper alignment of the fastener holes in the canister, bag and retaining flange as the fastener holes in the relatively flexible bag material tend to become easily displaced relative to the fastener holes in the canister and/or retaining flange. As a result, an assembly worker must either be dedicated to maintaining the fastener holes in proper alignment or else a worker will have to stop whatever else that worker was doing in order to realign the fastener holes in the bag with the fastener holes in the canister and in the retaining flange. This of course slows and increases the cost of the assembly process. Further, a requirement for human intervention to reeffect proper fastener hole alignment prevents implementation of a more fully automated assembly process.
Furthermore, each fastener is an entity in and of itself with each such fastener needing to be tightened to a specific torque, thereby complicating the assembly process. For example in order to better ensure safety in and proper functioning of air bag module assemblies, the component parts of the assembly, including fasteners, and the particulars of each such use of a component part is desirably recorded and tracked. Such recording and tracking operations, however, are undesirably complicated as the number of component parts of the assembly is increased. In view thereof, air bag module assemblies are generally preferably designed to minimize the number of component parts used therein.
In addition, common fasteners such as screws, bolts and rivets, include a protruding head portion. Thus in systems which utilize such fastening means, the system must be designed to allow for such protrusions. In inflatable restraint systems, however, space comes at a premium and thus such systems are preferably designed seeking to minimize space requirements.
Also, fasteners, specifically portions thereof such as the protruding head, can undesirably snag objects with which they come into contact with. The creation of such snags in an inflatable air bag not only detrimentally effects the aesthetics of the system but, dependent upon the extent and location of the snag(s) could jeopardize the proper functioning of the system.
Thus, there are a number of U.S. patents that at least in part relate to cushion attachment and retaining mechanisms which avoid or reduce the use of or reliance upon fasteners such as rivets, bolts, and screws and, in turn, avoid or reduce the occurrence of the problems associated with the use of such fasteners.
For example, U.S. Pat. No. 4,941,678, Lauritzen et al., issued Jul. 17, 1990, discloses a lightweight housing canister assembly wherein notches formed on the inner side of each of the walls of the reaction canister body form a bag retaining ring shelf for retaining a continuous attachment ring formed at the gas inlet opening of the inflatable bag. Without the use of some sort of fastener, the retaining of such a continuous attachment ring onto the bag retaining shelf could pose a problem.
U.S. Pat. No. 4,986,569 discloses an air bag attachment system comprising a canister having a shoulder on a peripheral edge flange for seating of a metal rod disposed in a channel in the air bag. The edge flange of the canister is reentrantly folded about the rod to retain the air bag on the canister. Upon bag deployment, the reentrantly folded flange of the canister would appear susceptible to unfolding and to subsequent release of the metal rod disposed in the air bag channel. In addition, the edge of such a folded flange of the canister would appear to contact the air bag upon deployment thereof. As such an edge can form a relatively sharp edge surface, contact of the bag therewith could likely result in a tearing of the bag fabric and consequent failure by the system.
U.S. Pat. No. 5,069,480 though relying on the inclusion of a multiple number of fasteners, e.g., rivets "196", in securing an air bag to a retainer, discloses an air bag retainer assembly which includes a pillow or air bag assembly including a pillow retainer to which is attached an inflatable pillow or air bag and which retainer is secured to the reaction housing assembly. Gas, supplied upon activation of a gas generator, will flow through openings provided in the retainer and into the pillow or air bag. The air bag is secured to the retainer by means of both:
a) a fastener such as a rivet inserted within openings through the fabric of the air bag and into a corresponding opening in the retainer, and PA1 b) a V-shaped hem sewn about the end of the bag and which upon movement of the hem and air bag forward engages and envelopes the circumferential edge of the retainer. PA1 a) securing a thickened peripheral gas inlet opening of an inflatable cushion in a channel portion of a cushion retainer to form a cushion/retainer subassembly, wherein the secured gas inlet opening forms a male mating member attachment insert; and PA1 b) inserting the male mating member attachment insert in a female mating sleeve portion of the reaction housing member to effect joinder of the subassembly with the reaction housing member. PA1 a) the thickened peripheral gas inlet opening of the inflatable cushion contains a bead material and PA1 b) the reaction housing member is at least in part made of an extruded metal with the sleeve portion integrally formed therewith.
U.S. Pat. No. 4,877,264 discloses the sewing into place, in the bag mouth, an elastomeric o-ring bead material. The bead material is configured and adapted to fit into a groove in the outer surface of a retainer ring. To effect engagement, the locking bead is stretched over a flanged upper lip portion of the retaining ring. The mouth of the bag is then permitted to contract back into the grooved portion of the ring.
Examples of other such patents include: U.S. Pat. No. 4,111,457 which discloses the use of a clamping ring to secure the edge of an air bag to the housing of the inflatable restraining device; and U.S. Pat. No. 5,058,919 which discloses an air bag module construction and assembly technique wherein a screen-shaped member is used to retain a folded air bag in the housing.
Thus, a relatively simple, low cost cushion attachment and retaining mechanism which: 1) avoids the use of fasteners such as rivets, bolts, and screws and the problems associated with the use of such fasteners, such as those identified herein and 2) which mechanism permits an easy adaptation to automated production and assembly is desired.